1. Field of the Invention
The present invention relates to an air-to-fuel ratio controlling system for internal combustion engines.
When it is desired to attain an effect of anti-pollution by exhaust gases of an automobile to a maximum extent in an improved anti-pollution engine or to attain an optimum cleaning effect of exhaust gases by a catalytic converter in an engine, an air-to-fuel ratio of air-fuel mixture fed to the engine must always be properly controlled. The present invention is thus intended to meet such a requirement.
2. Description of the Prior Art
In a prior art system of this type, an oxygen concentration in exhaust gases from an engine is sensed as an electrical signal and fed to a determination circuit in which an air-to-fuel ratio of air-fuel mixture is determined to change a path area of an adjusting air path which bypasses a throttle valve and a fuel nozzle of a carburetor, that is, the amount of air bypassed, for controlling the air-to-fuel ratio.
In this system, however, at a transition of the engine, particularly at the deceleration thereof, the air-to-fuel ratio of the air-fuel mixture decreases (that is, the air-fuel mixture becomes rich) resulting in mis-fire or after-burn of the engine, which in turn causes a problem in that a required air-to-fuel ratio cannot be attained and in addition an exhaust gas cleaning device such as a catalytic converter is deteriorated or thermally broken.